I'm going to be purchasing either a Marmot Hydrogen (30 degrees) or a Helium (15 degrees). My question is for those with experience with either of these bags: do you think the temperature ratings are about right, or are they generous?

I'm going to be purchasing either a Marmot Hydrogen (30 degrees) or a Helium (15 degrees). My question is for those with experience with either of these bags: do you think the temperature ratings are about right, or are they generous?

That's a very sujective question and answers could vary on any number of variables (metabolic rate, someone's 'nature', what you ate for dinner, what you wore, where you slept, etc, etc, etc). I have the Hydrogen (30*) and have used it inside a goretex bivy down to ~10-15*F and been quite cozy. I was also wearing expedition weight fleece tops and bottoms, a Patagonia Puffball Pullover, and a fleece hat. But like I said, I was warm, not just "barely hangin on".

While on the AT (more that two years earlier) I used a Marmot Arroyo (at that time the only difference between it and the now Hydrogen was the zip and materials) into the low 20's in shelters with only the expedition weight capilene and hat and was perfectly warm as well. If you've used an old-style Arroyo, I think that they are essentially the same warmth.

In general among my circle of friends, I've found that Marmot's high-end bags tend to be conservatively rated (meaning that they're warmer than they say they are). But like I've said, take this, and anything anyone else says about temp ratings, with a grain of salt.

While I wouldn't hesitate to bring my Hydrogen when I'm expecting 20*F weather (as long as I'm carrying adequate clothing), you might freeze to death at 40*F for all I know.

-Howie

I have the hydrogen and it is an excellent bag from all sides (lite-weight, compacts well, plenty of wiggle room, etc.) I have actually been in the bag into the low twenties/high teens and have slept well. I have to qualify this by stating that I sleep on the warm side so this may not be the case for you though. My wife has to sleep in a 10 degree bag to be comfortable on nights with temps in the twenties and thirties so go figure. The 30 degree reading I believe is acurate for most people though. You can't go wrong with the helium either if it is anything like the hydrogen.

Thanks for the feedback. I know how variable we all are as to metabolism, etc., but I remembered reading a review somewhere in which someone said he thought the temp rating on the hydrogen was generous, but I used an Aroyo for years and liked that bag a lot. Thanks again.